I don't think I've ever made any effort to try to talk in an upbeat voice. I try to honestly express how I'm feeling. I do use a stern voice when it comes naturally. I don't even try to be upbeat about stuff like telling ds to come get his shoes on. I just say it in a normal voice, or bored, or even a bit frustrated with waiting. I dunno...it's never seemed to affect ds negatively, and it's not like he hears a stern voice and immediately jumps.
When he was younger, I'm sure it sounded like I was commanding him to do simple things. But I wasn't, and he didn't take it that way.
But I don't often progress from upbeat to stern, trying to get ds to listen. Sometimes I do, but that would be out of frustration that ds isn't listening, and that doesn't feel good to me. I definitely prefer to totally change tactics after asking a couple times.